Description : In order that current should flow without causing excessive heating or voltage drop, the relay contacts should (a) have low contact resistance (b) be clean and smooth (c) be of sufficient size and proper shape (d) have all above properties
Last Answer : (d) have all above properties
Description : As shown in the illustration, once the "LV" relay is energized for operation, what contacts must remain closed to maintain the "LV" relay energized when the control lever is moved away from the "off" or "stop" ... . B. Reset contacts. C. Upper set of "LVa" contacts. D. Lower set of "LVa" contacts.
Last Answer : Answer: C
Description : When an operating motor is connected to the controller shown in the illustration, the a path of current flow through the circuit is ____________. EL-0010 A. 'L1', stop button, start button, coil 'CR', 'L2' B. 'L1' ... L2' D. 'L1', stop button, start button, 'CR' contact, 'M' contact, 'CR' coil, 'L2'
Last Answer : Answer: B
Description : As shown in the illustration, what is responsible for maintaining the "LV" relay energized when the master switch handle is moved away from the "off" position? EL-0102 A. "DBa" contact. B. Reset contacts. C. Upper set of "LVa" contacts. D. Lower set of "LVa" contacts.
Description : Which of the following statments is true of the illustrated motor controller? EL-0023 A. The low speed is used for starting the motor and when the controller automaticly shifts to High speed. B. The HOL relay ... D. If the overload relay opens for high speed the motor can still be run in low speed.
Last Answer : Answer: D
Description : The contacts operated by the D.C. relay coil shown in the illustration are located in the schematic diagram prints at coordinates ____________. EL-0100 A. '41Y' on this page B. '52M52M' and '52H35M' C. '57R' on this page D. '52N' on page '57R'
Description : When the series field relay "FR" of the winch circuit shown in the illustration is energized during dynamic braking the _______________. EL-0102 A. shunt Field Relay "FR-B.O." is de-energized and contacts ... . shunt Field Relay "FR-B.O." opposes the series coil's flux and sets the mechanical brake
Description : The vertical dotted line connecting the small circular symbols at coordinates '05L', '09L', '13L', '21L', '25L', etc., shown in the illustration, indicate that all _______________. EL-0100 A. contacts are ... board 'TB2' C. wires are grounded at both ends of the line D. wires have a common shield
Description : 'A-1', as shown in the illustration, is/are ____________. EL-0017 A. normally-closed overload relay contacts B. a double pole knife switch C. normally-open overload relay contacts D. a single pole knife switch
Last Answer : Answer: A
Description : Power necessary to operate the horn relay shown in the illustration ____________. EL-0093 A. comes from each station's magneto B. is supplied from a 115 volt source C. is conducted through the relay's contacts D. also lights lamps 'R' and 'T'
Description : Magnet chatter or 'pumping' occurring in a magnetic contactor can be caused by ______________. A. dirt or grease on pole faces B. mechanical interference in the contacts C. chattering contacts on the control relay D. magnetic lock out of the contacts
Description : If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, the probable cause may be _____________. A. excessive spring tension B. overvoltage C. excessive current D. welded contacts
Description : During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points
Description : The 'function generator' of the control circuit illustrated _______________. EL-0095 A. can be programmed to produce a non-linear output for a linear input depending on operating conditions B. is used for ... which or how many engines are needed for a required vessel speed D. all of the above
Description : The purpose of a magnetic relay is to _____________. A. open a circuit only in the event of overload B. remotely open and close contacts C. provide overcurrent protection during starting D. relay voltages at increased power
Description : Low voltage releases as used in some shipboard motor starter and control equipment will have which of the following characteristics? A. They trip circuit contactors when the motor starts to overspeed. B. ... coil of the starter. D. They allow the motor to restart upon restoration of normal voltage.
Description : The devices marked 'T' in the illustration are _____________. EL-0080 A. trouble alarm units whose contacts activate when problems arise either on starting or stopping of the motor B. topping ... contactor parts whose contacts start and stop the defrosting cycle of the compressor driven by the motor
Description : Mention any two applications of differential relay.
Last Answer : Protection of generator & generator transformer unit; protection of large motors and busbars .
Description : Interruption of large currents by relay requires (a) arc suppressing blow out coils (b) wide separation of the opened contacts (c) high speed opening of contacts (d) all of the above
Last Answer : (d) all of the above
Description : Overheating of relay contacts or contact born out is due to (a) slow making and breaking of load circuit contacts (b) foreign matter on the contact surface (c) too low contact pressure (d) all of the above
Description : What is used to clean the contacts of a relay?
Last Answer : A burnishing tool.
Last Answer : Overheating of relay contacts or contact born out is due to slow making and breaking of load circuit contacts, foreign matter on the contact surface, too low contact pressure.
Last Answer : In order that current should flow without causing excessive heating or voltage drop, the relay contacts should have low contact resistance, be clean and smooth, be of sufficient size and proper shape.
Description : Mention the properties of oil used in transformers.
Last Answer : The following are the desirable properties of transformer oil: -->It should be free from moisture --> It should have high dielectric strength --> It should have thermally stability and higher thermal conductivity -->It should be contaminated by temperature rise.
Description : Mention the properties of transformer oil.
Last Answer : Properties of transformer oil are, a) Colour – pale yellow. b) Moisture content -
Description : As shown in the illustration, the symbol is used in electrical drawings to designate a ____________. EL-0026 A. limit switch with one set of normally open contacts B. maintaining type ... type push button with a mechanical interlock D. normally closed contact held open mechanically by an interlock
Description : Regarding the illustrated electrical schematic, 'S1-P', 'S1-Q', and 'S1-R' represent ____________. EL-0016 A. capacitors B. normally-closed contacts C. normally-open contacts D. normally-closed pushbutton switches
Description : As shown in the illustration, all 'MS' contacts are opened and closed by means of ________. EL-0073 A. operating coils B. magnets C. manual operation of the master switches D. solenoid switches
Description : To stop the electric motor shown in the illustration, the stop button is depressed, causing ____________. EL-0012 A. coil 'MS' to become de-energized B. contacts 'CR1' and 'MR4' to open C. contacts 'MR1', 'MR2', and 'MR3' to open D. contacts 'MS1', 'MS2', and 'MS3' to open
Description : If the three-phase motor, shown in the illustrated schematic diagram, is running in the forward direction, which of the following actions must occur before the motor will reverse rotation? EL-0011 A. Normally-closed ... 'L1' and 'L3' must be interchanged via the 'R' contacts. D. All of the above.
Description : Refering to the illustrated schematic diagram, which of the following statements is true when the motor is running in the forward direction? EL-0011 A. Normally-open contacts '4-5' are closed. B. Current ... switch. C. Normally-closed contacts 'R' are open. D. The blowout coils must be closed.
Description : When the motor shown in the illustration is running and the stop button is pushed, which of the following statements will hold true? EL-0010 A. Coil 'M' will now be energized. B. Coil 'CR' will now be energized. C. Contact 'M' will close as contact 'CR' opens. D. Contacts 'M' and 'CR' will open.
Description : As shown in the illustration, which of the operations listed will happen when the 'jog button' is pushed? EL-0010 A. Coil 'CR' closes the normally open 'CR' contacts. B. Coil 'M' opens contact 'M'. C. Coil 'M' closes contact 'M'. D. Contact 'M' remains open despite the jog button being pushed.
Description : As shown in the illustration, which listed action will occur first when push button 'Q' is depressed? EL-0017 A. Contacts 'H-1', 'H-2' and 'H-3' close. B. Contact 'H-4' closes. C. Operating coil 'C' energizes. D. Switch 'R' opens.
Description : If the motor shown in the illustration will not start when 'Q' is depressed, which of the listed components should be checked FIRST? EL-0017 A. Fuses 'F-1' and 'F-2'. B. Operating coil 'C'. C. Contacts 'H-1', 'H-2', and 'H-3'. D. Contact 'H-4'.
Description : What is the main function in the use of a capacitor for starting a single phase motor? A. Reduce radio interference B. Split the phase to establish a rotating magnetic field C. Reduce the phase angle D. Prolong the life of the starting contacts
Description : After turning on the fluorescent lamp shown in the illustration, you note that the ends of the tube alternately glow and becomce dark without illuminating the center. The most obable cause for ... the lamp D. component 'B' contacts are opening and closing thus prohibiting sufficient current flow
Description : The illustration shows a fluorescent light fixture. The ends of the lamp alternately glow and become dark, but the tube will not light. The most probable cause is that ____________. EL-0081 ... start the lamp D. component 'B' contacts are opening and closing thus prohibiting sufficient current flow
Description : In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 6 reads line voltage, while the voltmeter reading between 2 and 6 reads 0 VAC. The problem is __________. EL- ... in the 'M' coil, 'Ma' contact/start switch or overload contacts D. fuse '10a' is blown
Description : In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in ... through varying loads in parallel or single operation D. the circuit breaker is closed for that generator
Description : When the operating handle is in the 'off' position, which master switch contacts for the winch shown in the illustration are closed? EL-0102 A. 'MS-DB & OL' B. 'MS-3, 5, 6, 7, & 8' C. 'MS-LVa & OL' D. 'MS-3, 7 & Reset'
Description : The winch shown in the illustration will not operate in any speed in the lowering direction and at an abnormal speed in 'first point hoist'. The possible cause is that _______________. EL-0102 A. ... '1M' in the power circuit are badly corroded D. master switch contacts 'MS6' have weak springs
Description : In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel ... event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity
Description : Which of the listed conditions occur when '4th point lower' is selected on the winch shown in the illustration? EL-0102 A. Master switch contacts '3', '4', '6', '8', '9', & '10' close. B. Contactors '2, 3, & 4M' and ' ... , '7', '8', and '9' close. D. Contactors '1 & 3M' and '1, 2, & 3A' pick up.
Description : Which of the listed conditions occur when selection is made for 'third point hoist' on the winch shown in the illustration? EL-0102 A. Master switch contacts '5', '6', '7', '8', and '9' close. B. Contactors '2M', ' ... ' and '2A' drop out. D. Master switch contacts '3','4', '6', '8', and '9' close.
Description : During maintenance of circuit breakers, _______________. A. always smooth roughened contact surfaces with a file B. never pass more than rated breaker current through the overload heater element C. ... wear and misalignment of main contacts D. assume heater elements installed are of correct size
Description : How long after energizing 'ATMX' at '41Y' shown in the illustration do the contacts of 'ATM' operate? EL-0100 A. 3 minutes B. 27 minutes C. 30 minutes D. 33 minutes
Description : Complete controller maintenance includes _____________. A. periodic testing of protective devices B. checking for loose or worn contacts and weak springs C. maintaining a sufficient supply of spare parts D. all of the above
Description : When 'selector switch' 'SEL8' shown in the illustration is in the 'TEST' position, contacts '3,4' and '7,8' are respectively ____________. EL-0100 A. open; closed B. closed; open C. open; open D. closed; closed
Description : In the system shown in the illustration, the station at section I is unable to signal any other station nor is any other station able to signal the station in section I. The station can, however, ring ... only a single station to respond to itself. D. The switch at component 'C' is stuck open.